Title Morphological Study of the Carpal Tunnel and the Ulnar Canal

Author(s) FUKUHARA, TOMOHIKO; HIRASAWA, YASUSUKE;TOKIOKA, TAKAO

Citation 日本外科宝函 (1988), 57(4): 267-275

Issue Date 1988-07-01

URL http://hdl.handle.net/2433/203966

Right

Type Departmental Bulletin Paper

Textversion publisher

Kyoto University

Arch Jpn Chir 57(4), 267～275, Juli, 1988

Morphological Study of the Carpal Tunnel

and the Ulnar Canal

ToMOHIKO FuKUHARAへYASUSUKEHIRASAWAへandT AKAO TOKIO KA本水

キDepartmentof Orthopedic Surgery, Kyoto Prefectural University of :VIedicine, Kyoto, Japan 本＊Departmentof Anatomy, Osaka Dental College, Osaka, Japan

Received for Publication, Apr. 25, 1988.

Summary

Ten adult upper limbs after the injection of the resin were cut into 5 mm cross-sections.

The morphology of the wrist joint, especially of the carpal tunnel and the ulnar (Guyon)

canal wぉ examinedunder the stereoscopic microscope.

The carpal tunnel departs from the palm gradually, from the inlet to the outlet, and the

thickness of the fiexor retinaculum increases and becomes maximum at the outlet.

The fiexor retinaculum, for surgical treatment of the carpal tunnel syndrome, must be

released completely to its distal part to secure complete release of the median nerve.

Since the ulnar canal itself has few bone elements, no tight connective tissue on the palmar

side except for the inlet portion, and no tendons passing through it, chronic mechanical irritation

is unlikely occur without chronic external trauma or mechanical narrowing such as by a tumor

or a fracture fragment.

Introduction

Peripheral nerves pass through tunnels (entrapment points) formed by the fascia, tendon

sheath, ligaments, and bone sulci as they run distally. Therefore, narrowing of these tunnels

for any reason may cause constriction of the nerves. Persisting mechanical irritation such as

that due to joint motion induces so-called friction neuritis, and progression of connective tissue

proliferation in and around of the nerve trunk results in irreversible fibrosis. If nerve fibers

become constricted the axonal flow distal to th巴entrapmentpoint is gradually impaired, causing

axonocachexia and, eventually, Wallerian degeneration.

Entrapment neuropathy is considered to be caused primarily by 1) mechanical compression

of the local n巴rvetrunk, 2) friction fibrosis secondary to chronic mechanical irritation, and 3)

anoxia due to circulation insu伍ciencyin and around the nerve trunk.

In entrapment neuropaty, unlike simple compression neuropathy, fibrosis in the nerve trunk

Key words: Entrapment neuropathy, Carpal tunnel syndrome, Ulnar (Guyon) canal syndrome, :V1ed Ulnar nerv e

索引語：絞括性神経障害，手根管症候群，尺骨管症候群，正中神経，尺骨神経．Present address: Department of Orthopedic Surgery, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo・ku,Kyoto 602, Japan.

268 日外宝第57巻第4号（昭和63年7月）

induced by chronic mechanical irritation, especially friction司 isone of the most important causative

factor.

The authors prepared the serial cross-sections, around the wrist JOint at 5 mm intervals, and

examined the morphology of the carpal tunnel and ulnar (Guyon) canal under the stereoscopic

microscope.

Tissue sections 50 μm in thickness were also prepared under the light microscope.

Methods

Using T ANIGUCHI-0HTA’s resin i吋巴ctionmethod acrylated resin was injected into brachial

artery from axillary region.

Ten adult upper limbs were cut into 5 mm cross-sections perpendicular to the axis using

BS-3000 (EXAKT, West Germany).

The morphology of the wrist joint, especially of the carpal tunnel and the ulnar canal was

examined under the stereoscopic microscope.

Fig. 1 shows the slice levels.

Tissue sections 50 μm in thickness stained with hematoxylin-eosin were also prepared and

studied under the light microscope.

Results

In the slice containing the proximal portion of the lunate, neither the carpal tunnel nor the

Slices Slice7 Slice6 Slices Slice4 Sl~ce3 Slice2 Slice1

Fig. 1. Slice levels of each section are shown.

MORPHOLOGICAL STUDY OF THE CARPAL TUNNEL AND THE ULNAR CANAL 269

Fig. ;2. In slice 1, at the proximal portion of the lunate, there was no obvious tunnel formation.

UN ulnar nerve, MN median nerve, U ulna, R: radius, L. lunate.

Fi邑.3. At the inlet of carpal tunnel and ulnar canal (slice 2), flevor retinacul um became obvious.

UN: ulnar nerve, MN median nerve, L: lunate, FR: flexor retinaculum, P pisiform,

N : navicular,

270 日外宝第57巻 第4号（昭和63年7月〉

Fig. 4. Carpal tunnel and ulnar canal at the middle portion of pisiform and navicular (slice 3).

P ・ pisiform, Tl ' triquetrum, C : capitate, N : navicular, UN : ulnar nerve, MN : median

nerve, FR: flexor retinaculum.

Fig. 5. At the distal portion of pisiform (slice 4), median nerve ran immediately dorsal to the flexor

retinaculum. Hypothenar muscle was observed medially to the ulnar canal.

UN: ulnar canal, MN median nerve, FR, flexor retinaculum, P: pisiform, Tl. tri-

quetrum, H: hamate, C: capitate, T2: trapezium, T3: trapezoid.

MORPHOLOGICAL STUDY OF THE CARPAL TUNNEL AND THE ULNAR CANAL 271

E’哩月f 毛，

曲目品、肉;;rn~ 一一一"""'!!E""' ‘ Fi昌.6. At this level (Slice 5) ulnar nerve divided into super五cialand deep branch in the ulnar

canal. But no obvious septum was observed. Concomitant artery and vein of each branch of nerve were observed.

sb: super五cialbranch of ulnar nerve, db deep branch of ulnar nerve, Tl: triquetrum, H : hamate, C: capitate, T3 : trapezoid, T2 : trapezium.

~：＇＞ゆS日 ；hJ A唱F E’

e’J .:--'• ≪i,,匂

校 〆ι… ペ－~ /J ，々."'

’a

慨 宮古吋午＼？ヨー均二持議事：；：：；：；

明おさ忌苧噛古~－） J守f"ザ句

、〈活動ム通よ記s認Fig. 7. At the level appearing hook of hamate (slice 6), flexor retinaculum became thicker. Piso-

hamate ligament was observed between super五cialand deep branches of ulnar nerve. Both branches accompanied their own artery and vein.

sb: super五cialbranch of ulnar nerve, db : deep branch of ulnar nerve, FR . flexor retinaculum, h: hook of hamate, MN : median nerve, I-I: hamate, C ・ capitate, T3: trapezoid, T2 : trapezium, 1 : 1st met乱carpalbone.

272 日外宝第57巻第4号（昭和63年7月）

Fi邑.8. At the level just proximal to the outlet of canals (slice 7), the thickness of the flexor retinaculum became maximum. Piso-hamate ligament became distinct.

ph : piso-hamate ligament, sb : super五cialbranch of ulnar nerve, db: deep branch of

ulnar nerve, FR : flexor retinaculum, h : hook of hamate, MN . median nerve, h : hamate, C : capitate, 1 . 1st metacarpal bone, T3 : trapezoid, T2 : trapezium,

Fig. 9. At the level of proxi.mal part of metacarpal bones (slice 8), flexor retinaculum disappeared.

Recurrent branch of median nerve was observed. Superficial branch of ulnar nerve was observed with concommitant artery and vein.

sb: super五cialbranch of ulnar nerve, MN‘median nerve, rn : recurrent branch of median nerve, 1-5 1st-5th metacarpal bone.

MORPHOLOGICAL STUDY OF THE CARPAL TUNNEL AND THE ULNAR CANAL 273

ulnar canal was observed (Fig. 1). At the inlet of the carpal tunnel and the ulnar canal, the

median nerve ran with 9 tendons immediately dorsal the flexor retinaculum. At this level, th巴

ulnar nerve ran with the ulnar artery and vein on the dorsal side of the flexor r巴tinaculum. The

carpal tunnel was separated from the ulnar canal by a thin septum (Fig. 3). In the slice passing

the middle part of the pisiforms and the navicular, the flexor retinaculum became distant from

the palm surface and was connected to the pisiform. Th巴 ulnarcanal penetrated the flexor

retinaculum to the palmar side. The palmar side of the ulnar canal was covered with fat tissue

(Fig. 4). In the level of the proximal trapezium and the distal pisiform, the flexor retinaculum

farther retreated from the palm surface and increased its thickness. The median nerve ran

inunediately dorsal the flexor retinaculum also at this level. The hypothenar muscle was observed

medially to the ulnar canal, which was not surrounded by tight connective tissue except for

the dorsal side (Fig. 5). In the slice containing the middle portion of the trapezium and th巴

distal portion of the triquetrum, the flexor retinaculum was further thickened. The ulnar nerve

divided into the superficial and deep branches, but no septum was observed between these branch-

es. Each of them ran with a artery and a vein. No large artery was observed around由巴

median nerve (Fig. 6).

In the slice containing the base of the 1st metacarpal bone and the hook of the hamate, the

thickness of the flexor r巴tinaculumwas further increased, and the carpal tunn巴1became more

distant from the palmar surface. The median nerve still ran immediately dorsal the flexor

retinaculum. A septum, continuous with hamate (piso・hamateligament) was observed b巴tween

the superficial and deep branches of the ulnar nerve (Fig. 7).

At the outlets of the carpal tunnel and the ulnar canal, the flexor retinaculum showed

a maximum thickness and connected the hook of the hamate with the trapezium. The median

nerve progressively flattened as it ran immediately dorsal the flexor retinaculum, and the piso-

hamate ligament became more distinct (Fig. 8). In the slice at the proximal part of the meta-

carpal bones, the flexor retinaculum disappeared, and the median nerve, which was iurther

flattend, ran near the palm. A branch of the median nerve (recurrent nerve) was observed.

Of the branches of the ulnar nerve, only the superficial branch was noted (Fig. 9).

Discussion

The carpal tunnel was formed by the carpal bones in its lateral and dorsal sides and by the

flexor retinaculum with its proximal end on the line between the na吋cularand pisiform and its

distal end on the line between the trapezium and the hook of the hamate on the palmar side.

In the carpal tunnel, a total of nine tendons, namely four each of the superficial and d巴ep

flexor tendons and the tendon of flexor pollicis longus, ran with the median ne町 e.

The flexor retinaculum increased its thickness as it approached the outlet of the carpal tunnel

(maximum at the outlet) and gradually became distant from the palmar surface.

The median ne町 eran immediately dorsal to the flexor r巴tinaculumwith no large artery in

the ca中altunnel, and approached the palm again after it left the carpal tunnel.

The floor of the ulnar canal was composed of the flexor retinaculum and piso司hamateliga-

274 日外宝第57巻第4号（昭和63年7月）

ロient.

The roof was composed of thin volar carpal ligament and fibers of palmaris brevis.

The hook of hamate formed lateral wall and the pisiform with tendinous fibers of flexor

carpi ulnaris the medial wall (SUNDERLAND）叫．

According to the authers’observation, the ulnar canal was located on the dorsal side of the flexor retinaculum at the inlet but soon penetrated the f!exor retinaculum to its palmar side. The

canal was formed medially by the pisiform and laterally by the hook of the hamate, but no tight

connective tissue was observed on the palmar sid巴 exceptfor the inlet portion.

In the ulnar canal, the ulnar nerve ran with the ulnar artery and vein, but no tendon was

present.

The ulnar nerve ran on the lateral side of the pisiform and immediately bifurcated into super-

ficial and deep branches, which were divided by a septum (piso-hamate ligament) (HAYES et al.,

196W>.

Median nerve palsy due to compression at the wrist was documented early by PAGET (1853)

and SCHULTZE (1890), and was shown by JONES (1895) to b~ caused by excessive motion of the

wrist joint4•7•8> ,

The role of the flexor retinaculum in this condition was first noted by MARIE and Forx

(1913) and was confirmed by surgical decompression by LEARMOUTH (1933)6>.

Median nerve compression is generally reported to be cured in more than 80% of the patients

by opening of the carpal tunnel with release of the f!exor retinaculum.

According to LMWLOH (1972), however, the flexor retinaculum partially remained in 62%

(21/34) of the patients showing poor outcome, and MACDONALD (1978) reported that the most

frequent complication was insu伍cientrelease of the f!exor retinaculum (33%) followed by palmar

branch injury (32%). Also POISEL (1974) observed that the recurrent branch of the median

nerve penetrated the flexor retinaculum in 23% of the patientsi,s>.

According to the authors' observation, the carpal tunnel departed from the palm from the

inlet to the outlet, and the thickness of the flexor retinaculum increased and became maximum at

the outlet.

These findings suggest that the flexor retinaculum must be released completely to its distal

part under direct observation, for surgical treatment.

Detailed deo:cription of the anatomy of the ulnar canal by GUYON (1861) and the first report

ofneuropathy caused in this canal by HUNT (1908) were followed by numerous case reportsa>

It can be stressed that the ulnar canal differs from the carpal tunnel in that the roof is weeker司

tendons and tendon sheaths are absent, and the ulnar nerve is accompanied by a major artery

and vein.

Attention should be made to the direct chronic mechanical irritation or stimuli to the ulnar

neurovascular bandle and to space occupying lesion such as a tumor or fracture fragments in the

canal.

MORPHOLOGICAL STUDY OF THE CARPAL TUNNEL AND THE ULNAR CANAL 275

References

1) Graham RA: Carpal tunnel syndrome. A statistical analysis of 214 cases. Orthop 6：・ 12831287, 1983. 2) Hirasawa Y, Tokioka T: Morphological feature of the entrapment points and their blood supply. (in Japanese)

J Jpn Orthop Associ 62 (2): 20 21, 1988. 3) Hunt JR: The thenar and hypothenar type of neural atrophy of the hand. Am J Med Sci 141: 224-241, 1911. 4) Jones HL: Note on paralyses of the upper extremity. St Barth's Hosp Rep 132 135, 1895. 5) Langloh ND, Linscheid RL: Recurrent and unreleaved carpal-tunnel syndrome. Clin Orthop 83: 41-47,

1972. 6) Learmonth JR: The principle of decompression in the treatment of certain disease of peripheral nerve.

Surg Cli North Am 13: 905-913, 1933.

7) Phalen GS : Reflection of 21 years experience with the carpaトtunnelsyndrome JAMA 212: 1365 1367, 1970. 8) Phalen GS: The carpal-tunnel syndrome, Clin Orthop 83: 29-40, 1972. 9) Sanderland, S: Nerve and nerve injury Livingston, 1978. 10) Zbrodowski A, Buchs JB: Blood supply of the median nerve in the carpal tunnel. The Hand 15: 310-316,

1983.

和文抄録

手根管および尺骨管の形態的研究

京都府立医科大学 整形外科学教室

福原知彦，平津泰介

大阪歯科大学解剖学教室

時間孝夫

血管内にレジンを注入した成人上肢10肢を用い， 下で充分に開放する必要があると考える．

5mmの間隔で連続切片を作製し，手関節近傍乙とに 尺骨管は骨性要素が少なく，入口部を除けば掌側は

手根管および尺骨管の形態の検索を行なった． 軟部組織でおおわれており，また店主も通過していない

手根管はその入口部から出口部lζ至る聞に徐々に手 ので，外部からの慢性の機械的刺激，腫湯や骨折など

掌面より遠ざかり，また屈筋支帯は徐々に厚さを増し の機械的狭窄因子が加わらない限り神経障害は生じに

出口部で最大となっていた． くいと考える．

手根管症候群の手術療法に際しては屈筋交帯を直視